Field of the Invention
The present invention relates to an ink supply apparatus including a reservoir tank and an ink jet recording apparatus.
Description of the Related Art
Recently, ink jet recording apparatuses including reservoir tanks have been widely used as production apparatuses. Such ink jet recording apparatuses can continue recording operations using ink in the reservoir tanks if the ink tanks become empty (hereinbelow, referred to as “stop-less recording”). In addition, the ink jet recording apparatuses can change the ink tanks during a period when the recording operations are continued using the ink in the reservoir tanks.
On the other hand, regarding the ink used by the ink jet recording apparatuses, ink components in the solution (ink) settle down by being left, and the ink concentration distribution in the ink tanks become uneven in some cases. Especially, such an issue is more likely to occur in the ink jet recording apparatuses using pigment ink. Thus, it is necessary for the ink jet recording apparatuses to regularly stir the ink in the ink tanks and the reservoir tanks.
For example, an ink jet recording apparatus discussed in Japanese Patent Application Laid-Open No. 2007-313830 (see FIG. 12A) includes an ink tank 130 and a sub tank 330′ (a reservoir tank) which are arranged vertically. Further, a first flow path (a flow path on an ink introduction needle 321 side) and a second flow path (a flow path on an air introduction needle 322 side) are disposed between the ink tank 130 and the sub tank 330′, and the ink tank 130 and the sub tank 330′ communicate with each other by these flow paths. Furthermore, a lower end of the first flow path is arranged lower than a lower end of the second flow path in the sub tank 330′ so that the ink flows from the ink tank 130 to the sub tank 330′.
Accordingly, air in the sub tank moves to the ink tank through the second flow path based on a water head difference, and also the ink in the ink tank 130 is automatically supplied to the sub tank 330′ through the first flow path.
According to the invention described in Japanese Patent Application Laid-Open No. 2007-313830, a pump mechanism (see FIG. 12B) including a piston 510 reciprocating in a cylinder 500 is disposed in the first flow path (the flow path on the ink introduction needle 321 side) as an ink stirring unit.
By the operations of the pump mechanism, the ink flows from the ink tank 130 to the sub tank 330′ through the first flow path 321, and further the ink reserved in the sub tank 330′ flows (returns) to the ink tank 130 through the second flow path 322. The operations of the pump mechanism are repeated as described above, so that the ink is circulated and stirred between the ink tank 130 and the sub tank 330′.
According to the recording apparatus described in Japanese Patent Application Laid-Open No. 2007-313830, the ink in the ink tank is moved bit by bit to the sub tank by the pump mechanism and diluted and stirred in the sub tank.
On the other hand, the movement of the ink from the ink tank to the sub tank generates a minute negative pressure in the ink tank, and the ink in the sub tank is returned again to the ink tank bit by bit by the minute negative pressure. An ink flow returning to the ink tank is weak, and a stirring (raising) effect is low with respect to the high concentration ink settled down in the bottom of the ink tank. Therefore, it is necessary to improve ink stirring efficiency in the ink tank and the sub tank.